Plasma surface treatment method and resulting device

ABSTRACT

The present invention provides a method for treating a surface of an object using, for example, a downstream region of a plasma source. The method includes a step of generating a plasma from a gas-C in a plasma source, where the gas-C includes a gas-A and a gas-B. Gas-A is selected from a compound comprising at least a nitrogen bearing compound or an other gas. The other gas is selected from a mixture of an element in group  18  classified in the atomic periodic table. Gas-B includes at least a NH 3  bearing compound. The method also includes a step of injecting a gas-D downstream of the plasma source of the gas-C. The method also includes a step of setting an object (having a surface) downstream of the gas-D injection and downstream of the plasma source. A step of processing the surface of the object by a mixture species generated from the gas-C in the plasma and the gas-D is included. The NH 3  bearing compound in the gas-C includes a NH 3  bearing concentration that is lower than an explosion limit of NH 3 , which is safer than conventional techniques.

CROSS-REFERENCES TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Ser. No. 60/078,321filed Mar. 17, 1998, commonly assigned and hereby incorporated byreference for all purposes.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to objects and their manufacture.More particularly, the invention is illustrated in an example using anovel combination of gases and a downstream plasma surface forselectively removing photoresist materials for substrates used insemiconductor integrated circuits. Merely by way of example, theinvention can be applied in the manufacture of other substrates such asflat panel displays, micro electrical mechanical machines (“MEMS”),sensors, optical devices, and others.

[0003] In the manufacture of objects such as integrated circuits,processing safety and reliability have been quite important. Fabricationof integrated circuits generally require numerous processing steps suchas etching, deposition, photolithography and others. In thephotolithography process, for example, a photoresist film of material isoften used to form patterns on thin slices of silicon or films that aredeposited on such silicon. After patterning, however, it is necessary toremove the photoresist film from the silicon using a hydrogen bearingcompound. Additionally, hydrogen bearing compounds are used in plasmatreatment of silicon surfaces. In some cases, hydrogen is used toterminate ends of silicon bonds. Hydrogen is also used to remove oxides.Numerous studies have been made in using a hydrogen bearing compound,and in particular a low temperature process using a reductive reactionfrom atomic hydrogen produced by a hydrogen gas molecule gas plasma. Forexample, an object such as a wafer or hard disk has a surface, which isto be processed at a certain area or reactor exposed to high energyspecies such as ions even in the plasma downstream system. This way ofprocessing occurs because lifetime of atomic hydrogen generated in theplasma is often short and can easily recombine into hydrogen moleculesoutside of the plasma discharge area. Thus, the conventional processoften cannot avoid damage caused by high-energy species such as ions andelectrons, decreasing the controllability of processing.

[0004] Numerous techniques using hydrogen for processing devices havebeen reported. As merely an example, a conventional process for ashingorganic material, which is carbonized by ion implantation, using atomichydrogen in a downstream plasma of hydrogen diluted by nitrogen orargon, has been reported by in a paper by S. Fujimura, H. Yano, J.Konno, T. Takada, and K. Inayoshi: Study on ashing process for removalof ion implanted resist layer, Process Symposium, Dry Process, ProcedureVol. 88-7, Honolulu, Hi., May, 1987 (The Electrochemical Society Inc.Pennington, 1988) pp. 126-133, which is incorporated herein by referenceherein. It also has been reported that a high concentration atomichydrogen is obtained in plasma downstream by the use of mixture ofhydrogen and water vapor as the source gas for the plasma in J. Kikuchi,S. Fujimura, M. Suzuki, and H. Yano, Effects of H₂O on atomic hydrogengeneration in hydrogen plasma, Jpn. J. Appl. Phys., 32, pp. 3120-3124(1993) (“Kikuchi, et al.”), which is incorporated by reference herein.Kikuchi et al. proposes a method to make an environment of a highconcentration of atomic hydrogen at a downstream region where theinfluence of substantially all high energy species such as ions,electrons, and photons generated by plasma discharge can besubstantially ignored.

[0005] Moreover, it was discovered that silicon native oxide could beeliminated at low temperature using NF₃ injected downstream of a H₂+H₂Oplasma. This has been reported by J. Kikuchi, M. Iga, H. Ogawa, S.Fujimura, and H. Yano, Native oxide removal on Si surface by NF3-addedhydrogen and water vapor plasma downstream treatment, Jpn. J. Appl.Phys., 33, 2207-2211 (1994). This silicon native oxide removal processwith NF₃-added hydrogen and water vapor plasma downstream treatmentachieved a removal of silicon native oxide at nearly room temperature invacuum environment and formation of hydrogen terminated silicon surface.Thus, the reported process can replace the conventional high temperaturehydrogen gas pretreatment of silicon epitaxy. J. Kikuchi, M. Nagasaka,S. Fujimura, H. Yano, and Y. Horiike, “Cleaning of Silicon Surface byNF₃-Added Hydrogen and Water-Vapor Plasma Downstream Treatment,” Jpn. J.Appl. Phys., 35, 1022-1026 (1996). Additionally, it was suggested to usethis method for the several applications of a silicon basedsemiconductor-manufacturing process such as cleaning of a contact holeof ULSI devices, J. Kikuchi, M. Suzuki, K. Nagasaka, and S. Fujimura.The silicon native oxide removal with using NF₃-added hydrogen and watervapor plasma downstream treatment 4. Extended Abstracts (The 44th SpringMeeting, 1997); The Japan Society of Applied Physics and RelatedSocieties, 1997, (29p-W6) in Japanese.).

[0006] The aforementioned technologies generally required introducing ahigh concentration of a hydrogen gas into a plasma. The highconcentration of hydrogen causes an absolute risk of an explosion.Accordingly, a high-level safe system has to be prepared for practicaluse of this technology. For example, restrictions of the use of rotaryvacuum pump with conventional vacuum pump oil should be prepared. Arequirement of a vacuum load lock system in order to prevent the leakingof hydrogen from reaction reactor also need be prepared. A furtherrequirement would include a high volume dilution inert gas system atexhaust pump gas in order to reduce the concentration of hydrogen lowerthan its explosion limit. Moreover, the system would also require ahydrogen gas leak-monitoring system, a fire extinguishing system, and analarm system for the inside of equipment or installed room itself. Thesesafety requirements will generally result in high costs to use thistechnology and it will become an obstacle to the growth of thetechnology in the industry.

[0007] From the above, it is seen that an improved technique offabricating a substrate in an easy, cost effective, and efficient manneris often desirable.

SUMMARY OF THE INVENTION

[0008] According to the present invention, a technique including amethod and device for the manufacture of treating objects is provided.In an exemplary embodiment, the present invention provides a noveltechnique for treating a surface of an object using a plasma treatmentapparatus.

[0009] In a specific embodiment, the present invention provides a methodfor treating a surface of an object using, for example, a downstreamregion of a plasma source. The method includes a step of generating aplasma from a gas-C in a plasma source, where the gas-C includes a gas-Aand a gas-B. Gas-A is selected from a compound comprising at least anitrogen bearing compound or an other gas The other gas is selected froma mixture of an element in group 18 classified in the atomic periodictable. Gas-B includes at least a NH₃ bearing compound. The method alsoincludes a step of injecting a gas-D downstream of the plasma source ofthe gas C. The method also includes a step of setting an object (havinga surface) downstream of the gas-D injection and downstream of theplasma source. A step of processing the surface of the object by amixture species generated from the gas-C in the plasma and the gas-D isincluded. The NH₃ bearing compound in the gas-C includes a NH₃ bearingconcentration that is lower than an explosion limit of NH₃, which issafer than conventional techniques.

[0010] In a specific embodiment, the present invention provides anapparatus for processing an object. The apparatus includes a chamber anda plasma discharge room coupled to the chamber. A susceptor holds theobject, i.e., wafer, display, panel. The plasma discharge room isdownstream from the chamber. The apparatus also has a first gas supplycomprising a gas A coupled to the plasma discharge room, where the gas Acomprises a nitrogen bearing compound. The apparatus also has a secondgas supply comprising a gas B coupled to the plasma discharge room,where the gas B comprises an NH₃ bearing compound. A third gas supplywith a gas D coupled between the plasma discharge room and the chamberalso is included. The present apparatus does not generally require loadlocks or the like, which are often used with conventional hydrogenprocessing tools.

[0011] The present invention achieves these benefits in the context ofknown process technology. However, a further understanding of the natureand advantages of the present invention may be realized by reference tothe latter portions of the specification and attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 is a simplified drawing of a system according to anembodiment of the present invention;

[0013]FIG. 2 is a simplified cross-sectional view drawing of anapparatus according to an embodiment of the present invention;

[0014]FIG. 3 shows a concentration of atomic hydrogen in a H₂O+N₂ gasplasma vs. H₂O ratio of total plasma gas flow according to an embodimentof the present invention;

[0015]FIG. 4 shows a simplified relation between an etching speed ofsilicon dioxide and an atomic hydrogen concentration in a downstreamarea using the system of FIG. 1;

[0016]FIG. 5 shows etching depth of SiO₂ as a function of gas flow ratioof water-vapor and nitrogen with water-vapor diluted with nitrogen mixedgas plasma due to 500 watt, 2.45 GHz microwave and added NF₃ into downflow section under a pressure 2.0 Torr and a processing time of 3minute;

[0017]FIG. 6 shows a dependence of etching depth of SiO₂ on the mixingratio of water vapor and nitrogen in a surface treatment using equipmentshown in FIG. 2, for example; and

[0018]FIG. 7 is a simplified cross-sectional view diagram of a barreltype plasma ashing system according to an embodiment of the presentinvention.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS

[0019] According to the present invention, a technique including amethod and device for the manufacture of treating objects is provided.In an exemplary embodiment, the present invention provides a noveltechnique for treating a surface of an object using a plasma treatmentapparatus.

[0020] In a specific embodiment, the invention relates to a surfacematerial treatment method with use of the plasma producing atomichydrogen, for example. The invention also relates to a surface treatmentmethod using atomic hydrogen which is produced by a plasma. In analternative embodiment, the present invention uses a catalytic action ofnitrogen, helium, neon, argon, krypton, xenon and/or radon, as well asother elements, as a part of a plasma source gas. The invention alsouses a step of applying under a downstream plasma method which hasfeatures of being substantially free from physical surface damage. Insome of these embodiments, the present invention also reduces orminimizes inappropriate active species for the purpose of treatment,thereby providing a more efficient and effective process. Accordingly,the present invention can provide advantages such as decreased costs andincreased safety in surface treatment of a downstream plasma generatingatomic hydrogen, for example.

[0021] For easier reading, we have prepared the following list of itemsand their names, which are shown in the FIGS. for referencing orcross-referencing purposes. These names are merely shown forillustration purposes and should not limit the scope of the claimsherein. One of ordinary skill in the art would recognize othervariations, modifications, and alternatives.

[0022]1. #1 Gas inlet

[0023]2. Microwave guide

[0024]3. Microwave cavity

[0025]4. #2 Gas inlet

[0026]5. Chamber

[0027]6. Treatment room

[0028]7. Silicon substrate

[0029]8. Exhaust

[0030]11. Plasma discharge room

[0031]12. Gas-A supply unit

[0032]13. Gas-B supply unit

[0033]14. Fitting

[0034]15. Microwave generator

[0035]16. Wave guide

[0036]17. Microwave cavity

[0037]18. Nozzle

[0038]19. Gas-D supply unit

[0039]20. Fitting

[0040]21. O-ring

[0041]22. Treatment room

[0042]23. Treatment material

[0043]24. Treatment stage

[0044]25. SiC heater unit

[0045]26. Vacuum Exhaust port

[0046]27. Loading & Unloading port

[0047]28. Inside wall

[0048]31. Quartz reaction tube

[0049]32 a, 32 b. Electrode

[0050]33. RF generator

[0051]34. Wafer carrier

[0052]35. Wafer

[0053]36. Cover

[0054]37. Aluminum etch tunnel

[0055] Again, the above list of names are merely shown for illustrativepurposes. These names are not intended to limit the scope of the claimsherein.

[0056] Before proceeding to the details of the embodiments of thepresent invention, it may be helpful to fully understand some of theadditional limitations with conventional processing techniques. Asmerely an example, in an attempt to solve some of the risks associatedwith the above hydrogen gas techniques, Japanese Patent published underKOKAI H6-338578, which is based upon the paper above (J. Kikuchi, M.Nagasaka, S. Fujimura, H. Yano, and Y. Horiike, Cleaning of SiliconSurface by NF₃-added Hydrogen and Water-Vapor Plasma DownstreamTreatment, Jpn. J. Appl. Phys., 35, 1022-1026 (1996)), describes analternative technique. It has been suggested that the capability ofremoving silicon native oxide by adding NF₃ gas from the down steamregion of hydrogen containing gas plasma. The definition of “gascontaining hydrogen” claimed in item number 1 and 4 in this officialpatent report, is not clear, however. The paper indicated an achievementof the objective purpose due to the reaction of atomic hydrogen and NF₃.

[0057] Taking this in a broad sense, this suggests that a silicon nativeoxide layer would be removed by injecting NF₃ into the downstream of anyplasma, which is generated with a gas containing hydrogen atoms as itselement and produces atomic hydrogen. Therefore, if the same result ofsurface treatment in quoted paper is achievable with using H₂O moleculeplasma, which is generating atomic hydrogen, issues of safety andeconomical requirement indicated above, is solved. Additionally, watervapor is indicated, to carry a hydrogen atom described in the abovequoted paper.

[0058]FIG. 1 shows a plasma down stream process system using a quartztube similar to the FIG. in the official patent report KOKAI H6-338578.Using this system, for example, a process for trying to etch siliconthermal oxide set at a down flow region of plasma has been performedunder these following conditions. (Process time 30 minute, Processingpressure 1 Torr, 30 sccm H₂O as plasma source gas, 50 watt 2.54 GHzmicrowave as plasma generating source energy, and 5 sccm NF₃ added fromdown flow region of plasma.) A decrease in the thickness of the oxidewas not detected in the measurement by ellipsometry. Additionally, thesilicon wafer surface with a native oxide did not turn either fromhydrophilic to hydrophobic after the treatment. This meant that thenative oxide was not removed. The process was tested under differentoperation conditions with changing pressure from about 0.5 Torr to about3.0 Torr and changing flow rate of 10 sccm H₂O and 10 sccm NF₃. Theresult showed, however, no evidence of silicon dioxide etching.

[0059] The native oxide was not removed even using the equipment shownin FIG. 2 and got thicker in size to apply to practical treatment, underthe following conditions: 100 sccm H₂O, 100 sccm NF₃, 500 watt 2.54 GHzmicrowave power, processing pressure 1 Torr; and process time 10minutes. The result showed there is no evidence of removing nativesilicon dioxide.

[0060]FIG. 3 shows the dependence of a concentration of atomic hydrogenin a H₂O+N₂ gas plasma on an H₂O flow ratio to total gas flow. Theconcentration of atomic hydrogen in the plasma was measured using aactinometry method. Concrete conditions of the actinometry of atomichydrogen are described in J.VAC. Sci. Technol. B, 9, 357-361 (1991). Theresult shows that the highest concentration of atomic hydrogen wasobserved at 100% H₂O and the concentration of atomic hydrogen decreaseswith decreasing in H₂O ratio monotonously.

[0061] Above experimental results indicate that an etching reaction ofsilicon dioxide as described in the official patent report KOKAIH6-338578 does not occur in the system with a 100% H₂O plasma and NF₃injection to a downstream region, through atomic hydrogen is surelygenerated in the plasma. Thus, an altered process with NF₃ injectioninto the downstream of an water vapor plasma as the source of atomichydrogen does not etch silicon dioxide though the process satisfies thenecessary and sufficient condition which is the existence of atomichydrogen and NF₃ and is described in the official patent report KOKAIH6-338578. Therefore, this process could not achieve solving the issuesof safety and economical requirement.

[0062] In order to solve the above limitations, the relationship betweenthe etch velocity of silicon dioxide and hydrogen atom concentration indownstream area was investigated with the system shown in FIG. 1.

[0063] An experiment has been done as follows.

[0064] a) Generating a plasma with H₂O and N₂ mixed gas with a total gasflow of 30 sccm and 2.54 GHz Microwave of 50 watts.

[0065] b) Injecting NF₃ of 5 sccm into the downstream of the plasma.

[0066] c) Estimating the concentration of atomic hydrogen at 1 Torr by acalorimetry method using a shielded thermocouple, which is covered withquartz except at the tip and inserted into the area where object wouldbe set. The calorimetry method to measure atomic hydrogen flow isdescribed in, for example, “Young C. Kim and Michel Boudart,Recombination of O, N, and H Atoms on Silica: Kinetics and Mechanism,Langmuir, 7, 2999-3005 (1991), and L. Robbin Martin, “Diamond filmgrowth in a flowtube: A Temperature Dependence Study”, J. Appl. Phys.,70, 5667-5674 (1991)”.

[0067] d) Heating a certain place of the tube up to 500 degree Celsiusbetween the NF₂ injection point and the point where the object would beset. (Heating increases the reaction rate between atomic hydrogen andNF₃ to increase etching velocity. As the result, error in measurement inetching depth is reduced or minimized.)

[0068] e) measuring etching depth of the samples treated under severaldifferent operation conditions.

[0069] A flow rate of each gas is shown in FIG. 4 near by measurementpoint. Number on the left side of “:” indicates H₂O flow rate and thaton the right side of “:” indicates N₂ flow rate. A unit of gas flow ismeasured in sccm.

[0070] In FIG. 4, the concentration of the hydrogen atom is normalizedappropriately. From FIG. 4, it is clear that silicon dioxide is notetched in the treatment in 1 Torr with H₂O of relatively highconcentration in the H₂O and N₂ mixed gas (from 100% to 33% ) thoughatomic hydrogen exists at the point where the objects have been set.Under the condition of H₂O concentrations lower than 17% (H₂O flow rateis less than 5 sccm), however, silicon dioxide etch was observed and theconcentration of atomic hydrogen was also relatively higher than thatunder the condition with high H₂O mixing ratio.

[0071]FIG. 3 shows that the concentration of atomic hydrogen in theplasma increases with the mixing ratio of H₂O ratio in the mixed gas,thus the connection of atomic hydrogen in plasma at the H₂O mixing ratioof 17% is almost {fraction (1/20)}of that at 100% H₂O.

[0072] Moreover, the concentration of atomic hydrogen in the plasma atH₂O of 17% where that in the downstream was the highest is about{fraction (1/100)}of atomic hydrogen concentration in the plasma at 100%H₂O. On the other hand, the concentration of hydrogen atom in thedownstream at 7% H₂O is almost 13 times as large as that at 100% H₂O.These results seem to show that nitrogen generated atomic hydrogen. Thedisassociation ratio of 100% H₂O gas by 2.54 GHz microwave discharge isthe order of ten. See L. Brown, J.Phys. Chem., 71, 2429 (1967). Eventaking into consideration of the difference in plasma conditions, adisassociation ratio of H₂O in this experiment would still be severalpercent. If H₂O can carry atomic hydrogen toward a down flow regionwithout a decrease in the amount of atomic hydrogen independently ofoperating conditions, the concentration of atomic hydrogen in thedownstream would reflect that in the plasma. Thus, the fact that thenumerical ratio of atomic hydrogen concentration at the 7% H₂O to thatat the 100% changes from {fraction (1/100)}to 13 with shift in themeasurement position from the plasma to the downstream is not convinced,even if nitrogen disassociates water vapor and increases theconcentration of atomic hydrogen.

[0073] Consequently, it is a reasonable interpretation that the effectof water vapor on atomic hydrogen transportation reported in the paperwritten by J. Kikuchi, S. Fujimura, M. Suzuki, and H. Yano is effectivein the condition with a relatively lower H₂O mixing ratio in plasmasource gas and ineffective in the condition with H₂O mixing ratio closeto 100%, because hydroxyl radical (OH) and atomic oxygen (O) generatedin the plasma quench atomic hydrogen by recombination between them.(When the small amount of H₂O was mixed into H₂, OH or O has a higherpossibility to collide with a hydrogen molecule instead of atomichydrogen, then OH and O abstract a hydrogen atom from hydrogen moleculesand generate H₂O and OH and one free atomic hydrogen is simultaneouslyproduced. In this result to be produced is a free hydrogen atom fromhydrogen molecule.) Therefore, these experiments result that thecarrying mechanism of atomic hydrogen from plasma to downstream withmixing nitrogen up to be majority in a N₂+H₂O mixing gas as a plasmasource is different from that described in the official patent reportKOKAI H6-338578 and some species with catalysis made in the plasma fromthe nitrogen molecule probably caused the above phenomena that atomicconcentration in the downstream at H₂O mixing of several percent waslarger than that at 100% H₂O.

[0074] Experimental results in 1 Torr shown in FIG. 4 seems to also showthat higher atomic hydrogen concentration induces larger velocity ofsilicon dioxide etching. For example, however, silicon oxide was etchedby 13 A depth during 5 minutes of treatment under the condition wherethe treatment pressure was 2 Torr. The flow rate of water vapor andnitrogen was 2 and 28 sccm and not etched under the condition where thetreatment pressure was 1 Torr and the flow rate of water vapor andnitrogen was 10 and 20 sccm, though the concentration of atomic hydrogenin the former treatment condition was about ⅛of that in the latter. Inthe process performed using a gas mixed with a small amount of watervapor and nitrogen, therefore, the velocity of silicon dioxide etchingcaused by NF₃ injection into the downstream is not always in proportionto the concentration of atomic hydrogen. Taking consideration into thefact that the silicon dioxide etching does not occur depending upon theoperating condition in spite of existence of enough amount of atomichydrogen, this result concludes that silicon dioxide etching in thisH₂O+N₂ process does not mainly based on the effect of atomic hydrogenand NF₃ as shown in the official patent report KOKAI H6-338578 and iscaused through some other mechanism.

[0075] In FIG. 4, the operation condition giving acceptable etching rateof silicon dioxide distributes in the area showing that the flow rate ofnitrogen is far larger than that of water vapor in the mixed gas. It isknown that many excited nitrogen molecules with long life-time at ameta-stable energy state of which potential energy is about 10 eV areproduced in plasma. The potential energy of these nitrogen molecules isenough to disassociate H₂O and NF₃. This suggests that the etchingspecies might be produced by another reaction such as that between H₂Oand NF₂ instead of the reaction between the hydrogen atom and NF₃. Infact, etching did not occur when N₂ and NF₃ were injected into thedownstream of a 100% H₂O plasma, then few exited nitrogen existed in thedownstream. Therefore, though the accurate mechanism is not clear, it isseen that the etching using the mixed gas of nitrogen and a little watervapor is mainly caused by the catalytic effect of nitrogen throughplasma not caused by the mechanism depending on the reaction betweenhydrogen atom and NF₃ and described in the official patent report KOKAIH6-338578.

[0076] If the catalytic effect of nitrogen at meta-stable state makes itpossible to use H₂O as the source of the hydrogen atom, other inertgases having long life metastable energy state, such as Helium, Neon,Argon, are also available. Actually, the silicon dioxide etchingphenomena has been confirmed in the treatment that NF₃ was injected intothe downstream of a plasma generated using a gas composed by 90% Argonand 10% H₂O as a plasma source gas, though its etching rate wasrelatively smaller than that using the mixed gas of nitrogen and a fewpercent of water vapor.

[0077] This effect suggests that NH₃ can be used for this processinstead of H₂O. NH3 also has risk of explosion. In this process,however, the concentration of the catalytic species can be much largerthan that of process species such as water vapor. Namely, for example,nitrogen containing NH₃ whose concentration is lower than its explosionlimit. Actually, as shown in FIG. 6, lower concentration of NH₃ innitrogen brought higher etching rate. The explosion limit of NH₃ inatmosphere is based predominantly on concentration. Taking gas pressurein the vacuum pump and at the exhaust port into consideration, it ispreferable to use NH₃ at lower concentration than the explosion limit atatmosphere.

[0078]FIG. 2 shows the equipment for this invention. As shown is aplasma discharge section 11 for a plasma source gas made of such asquartz or alumina. Reference numeral 12 is the Gas-A supply unit andnumeral 13 is the Gas-B supply unit both of which are structured withmass flow controller, valve and filter. Mixed Gas-C, which is mixed withGas-A provided Gas-A supply unit 12 and Gas-B provided Gas-B supply unit13, is introduced into plasma discharge room 11 through the fitting-14.Mixed Gas-C introduced into the plasma discharge room 11 is dischargedinto plasma by microwave, which is supplied to microwave cavity-17through microwave guide-16 from microwave generator-15. The nozzle 18 toadd another gas is set at a suitable point in the downstream region ofthe plasma discharge area in the plasma discharge room 11. Gas-D isinjected into plasma downstream through the fitting-20 from Gas-Dsupplier unit-19. Gas-D supply unit is structured with mass flowcontroller, valve and filter. Plasma discharge room 11 is connected withtreatment room 22 with O-ring 21. The surface of object 23 which placedinside of the treatment room 22, is processed by the gas which isprepared by discharged Gas-C and injected Gas-D. The object 23 is placedon stage 24 and Si-C heating unit 25 is instrumented at upper section ofstage 24 in order to heat up the object 23. The treatment room 22 hasvacuum exhaust port 26 and connected to the rotary vacuum pump, which isnot showed in this schematic. The treatment room 22 also has thematerial transport port 27 in order to load and unload the object. Innerwall part 28 can be set inside of treatment room 22 in order to protectthe wall side of the treatment room or any other reason.

EXAMPLES 1. First Example

[0079]FIG. 5 shows the dependence of etching depth of SiO₂ on the mixingratio of water-vapor and nitrogen in the surface treatment using theequipment shown in FIG. 2. In this treatment, NF₃ of 100 sccm wasinjected into the downstream of N₂+H₂O plasmas discharged by 2.45 GHzmicrowave of 500 W and 6 inch silicon wafers covered by silicon dioxideas etching sample were placed in the downstream of the NF₃ injectedpoint. The maximum etching rate was obtained in the treatment with 5%water vapor but no etching occurred in the treatment with higher watervapor mixing ratio than 25%.

[0080] In addition, native oxide removal was confirmed by the resultthat the hydrophilic surface of a 6 inch Si wafer covered by nativeoxide was turned to hydrophobic after 3 minutes of downstream treatment.Then microwave power was 500 W, pressure was 2.0 Torr, flow rate of NF₃was 100 sccm, and flow rate of water vapor and nitrogen was 10 sccm and190 sccm.

2. Second Example

[0081]FIG. 6 shows dependence of etching depth of SiO₂ on the mixingratio of water vapor and nitrogen in the surface treatment using theequipment shown in FIG. 2, for example. In this treatment, NF₃ of 100sccm was injected into the downstream region of N₂+NH₃ plasmasdischarged by 2.45 GHz microwave of 500 W and 6 inch silicon waferscovered by silicon dioxide as etching sample were placed in thedownstream of the NF₃ injected point. Nitrogen gas containing lowerconcentration of NH₃ than a selected percentage based upon FIG. 6.served good etching result.

[0082] Additionally, native oxide removal was also confirmed by theresult that the hydrophilic surface of a 6-inch silicon wafer covered bynative oxide was turned to hydrophobic after 3-min downstream treatment.Then microwave power was 500 W, pressure was 4.0 Torr, and flow rates ofNF₃, NH₃, and nitrogen are shown in FIG. 6.

3. Third Example

[0083] Silicon substrate placed on the treatment heat stage in theequipment shown in FIG. 2 is processed in downstream of a nitrogenplasma with 5% of water-vapor (10 sccm). Flow rate of nitrogencontaining 5% of water vapor was total 200 sccm. Applied microwave (2.45GHz) was 500 W to generate plasma. In this treatment, silane gas of 5sccm was injected at the downstream. Substrate temperature was kept at450 degree C during processing and treatment time was 1 hour underpressure at 2 Torr. By the processing, certain deposited film was formedon the silicon wafer surface and the surface of the film washydrophilic.

[0084] After dipping this sample into 5% of HF diluted solution for 1minute, the silicon surface became the hydrophobic. This indicates thatthe deposited material must be some kind of silicon-oxide-material.

4. Fourth Example

[0085] Silicon substrate placed on the treatment heat stage in theequipment shown in FIG. 2 is processed in downstream of a nitrogenplasma with 5% of water-vapor (10 sccm). Flow rate of nitrogencontaining 5% of water vapor was total 200 sccm. Applied microwave (2.45GHz) was 500 W to generate plasma. In this treatment, ethyl alcohol of 5sccm was injected at the downstream. Substrate temperature was kept at600 degree C during processing and treatment time was 3 hr. By thistreatment, silicon wafer surface was discolored by a deposited film. Inorder to probe what this deposited material was, the sample was treatedwith plasma ashing system.

[0086]FIG. 7 shows the barrel type plasma ashing system is used toprocess wafer 35 on the wafer carrier 34 by oxygen plasma which isgenerated inside of quartz reaction tube 31 induced oxygen and suppliedRF power into the electrode 32 a and 32 b from RF generator 33. Wafer 35is load and unload at the part of open side of quarts tube 31, and usecover 36 at the processing time to cover quartz open side. Aluminum etchtunnel 37 is also available. Previous processed Si wafer with adeposition film was processed with this type of oxygen ashing systemunder conditions of oxygen gas flow 500 sccm, 1 Torr and 300 watt RFpower for 30 minutes. This processing stripped previously observeddeposited material. This is the indication that previous depositmaterial should be some type of carbon content material such asamorphous carbon or diamond like carbon. The result shows that thismethod can be used to produce carbon composite material film includediamond.

[0087] As above description, surface treatment in which atomic hydrogenwas the one of the necessary species is realized by the use of a gasmixed a gas containing essentially water vapor and a gas containingnitrogen, helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe)and/or radon (Rn), through the catalytic effect induced on nitrogen,helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe) and/orradon (Rn) by the plasma, though water vapor was used for the source ofatomic hydrogen. Accordingly, this invention makes it possible toinexpensively and safely use the atomic hydrogen surface treatmentwithout special safety protection system and circumstance.

[0088] For example, in comparison with conventional water vapor addedhydrogen plasma system, this technology can substantially eliminate theload lock module, object transfer system specialized to load lockenvironment, pumping package applicable to hydrogen evacuation, exhaustgas treatment system, safety and alert system, and other hardware. Thus,this invention provides the cost reduction of this system over10,000,000 yen per unit (in 1998) depending on the purpose of system andthe condition of operation.

[0089] While the above is a full description of the specificembodiments, various modifications, alternative constructions andequivalents may be used. Therefore, the above description andillustrations should not be taken as limiting the scope of the presentinvention which is defined by the appended claims.

What is claimed is:
 1. A method of surface treatment of materials at adownstream region of a plasma source, said method comprising steps of:generating a plasma from a gas-C in a plasma source, said gas-Ccomprising a gas-A and a gas-B, said gas-A selected from a compoundcomprising at least a nitrogen bearing compound or an other gas, saidother gas being selected from a mixture of an element in group 18classified in the atomic periodic table, said gas-B comprising at leasta NH₃ bearing compound; injecting a gas-D downstream of said plasmasource of said gas C; setting an object downstream of the gas-Dinjection and downstream of said plasma source, said object comprising asurface; and processing said surface of said object by a mixture speciesgenerated from said gas-C in said plasma and said gas-D; wherein saidNH₃ bearing compound in said gas-C includes a NH₃ bearing concentrationthat is lower than an explosion limit for NH₃ gas.
 2. The method ofclaim 1 wherein said object is a semiconductor wafer, said semiconductorwafer including a thin layer of oxide thereon, said NH₃ bearing compoundforming an entity that substantially maintains said thin layer of oxideon said semiconductor wafer.
 3. The method of claim 1 wherein saidspecies comprises atomic hydrogen.
 4. The method of claim 1 wherein saidprocess occurs in an apparatus that is substantially free from a loadlock module.
 5. The method of claim 1 wherein said other gas comprisesone selected from helium, neon, argon, krypton, xenon, or radon.
 6. Themethod of claim 1 wherein said nitrogen bearing compound is selectedfrom N₂ or NF₃.
 7. The method of claim 1 wherein said plasma ismaintained by a microwave source.
 8. The method of claim 1 wherein saidplasma is provided in a microwave cavity.
 9. A method of surfacetreatment of materials at a downstream region of a plasma source, saidmethod comprising: generating a plasma from a gas-A and a gas-B, saidgas-A selected from a compound comprising at least a nitrogen bearingcompound and said gas-B comprising at least a NH₃ bearing compound;injecting a gas-D downstream of said plasma source of said gas A and gasB; setting an object downstream of the gas-D injection and downstream ofsaid plasma source, said object comprising a surface; and processingsaid surface of said object by a mixture species generated from said gasA and gas B in said plasma and said gas-D; wherein said NH₃ bearingcompound is lower than an explosion limit for NH₃ gas.
 10. The method ofclaim 9 wherein said gas D is selected from a silane, an alcohol, andNF₃.
 11. The method of claim 9 wherein said species comprises atomichydrogen.
 12. The method of claim 9 wherein said process occurs in anapparatus that is substantially free from a load lock module.
 13. Themethod of claim 9 wherein said nitrogen bearing compound is selectedfrom N₂ or NF₃.
 14. The method of claim 9 wherein said plasma ismaintained by a microwave source.
 15. The method of claim 9 wherein saidplasma is provided in a microwave cavity.
 16. Apparatus for processingan object, said apparatus comprising: a chamber; a plasma discharge roomcoupled to said chamber, said plasma discharge room being downstreamfrom said chamber; a first gas supply comprising a gas A coupled to saidplasma discharge room, said gas A comprising a nitrogen bearingcompound; a second gas supply comprising a gas B coupled to said plasmadischarge room, said gas B comprising an NH₃ bearing compound; a thirdgas supply comprising a gas D coupled between said plasma discharge roomand said chamber; and a susceptor in said chamber for holding an objectto be processed.
 17. The apparatus of claim 16 wherein said gas D isselected from a silane, an alcohol, and NF₃.
 18. The apparatus of claim16 wherein said apparatus is substantially free from a load lock module.19. The apparatus of claim 16 wherein said nitrogen bearing compound isselected from N₂ or NF₃.
 20. The apparatus of claim 16 wherein saidplasma is maintained by a microwave source.